1. Field of the Invention
The invention relates to a sport boot constituted by an upper and a shell base connected and journalled to one another in the zone corresponding to the joint of the wearer's ankle, and its object is a device for coupling the upper to the shell base in the dorsal area of the boot. This device is adapted to determine the bending conditions of the upper with respect to the shell base.
2. Background and Material Information
Known boots of this type, especially ski boots, generally have an upper and a shell base that are journalled to one another about linkage axes in the zone corresponding to the wearer's ankle, where they are joined by at least a partial nesting on one another. Conventionally, the nesting is made through the lower edge of the upper that covers a collar formed by an extension of the wall of the shell base, which ensures a proper imperviousness. This collar, which is more or less flexible and high, is centered in the dorsal zone of the heel of the shell base on both sides of the journal axes of the upper, on the one hand, and is associated with a transverse edge on which the lower edge of the upper takes support when the upper is pivotally rearwardly biased, on the other hand. The junction zone thus arranged between the upper and the shell base makes it possible to limit the rearward bending of the upper and opposes a certain resistance to its forward bending. Indeed, because it covers the collar extending from the shell base, its forward pivoting is made possible only if the elastic deformation of the collar is induced, at least in the zone comprised between its journal axes and the dorsal zone of the heel of the shell base, and if the frictional forces resulting therefrom are overcome. To this end, the force applied on the front portion of the upper, in correspondence with the tibial zone of the skier, must be greater than the resisting force provided by the collar which cooperates with the rear portion of the upper; this collar therefore constitutes a means for controlling the bending during the stress. Furthermore, since the collar is encircled by the lower rear edge of the upper on both sides of the journal axes thereof, the resultant force produced to cause its forward bending is obliquely transmitted from the upper toward the tip of the shell base along a direction that is always oriented substantially perpendicular to the journal axes of the upper, i.e., practically always in the longitudinal axis of the boot. The collar thus associated with the journal axes of the upper therefore constitutes a means for controlling the bending of the upper that occurs in the direction of the force transmitted toward the shell base.
These boots are relatively satisfactory because they have a very simple structure and are relatively impervious, easy to manufacture and, therefore, inexpensive, and because the flexibility of the upper therein is progressive during the stress and is obtained by a pulling effect on the dorsal zone of the boot, which is a factor of comfort for the skier. Of course, in so doing, the force applied on the front portion of the upper by the skier is distributed over a large enveloping surface extending along the tibial zone and on both sides thereof, resulting in the absence of a hard spot or localized pressure, which are often noticed on boots in which the resisting force is obtained by a pushing effect on the front portion of the boot, between the upper and the shell base.
However, the performance level of these boots remain insufficient when intended for experienced skiers who wish to master and refine their technique for competition, cross country skiing on any snow, or exhibition skiing, and mostly for transmitting maximum power, i.e., of force, in their supports on the upper to optimize the pressures of ski-snow contact, directional effects, etc.
It is thus noted, for example, that the upper of these boots is really not limited in forward pivoting, especially for preventing accidents following an extreme dorsal bending or dorsibending of the skier's ankle, such as rupture of ligaments, tendons, or tear of muscles. Indeed, nothing firmly opposes the forward pivoting of the upper, in fact, the upper reaches its bending limits only when the front lower edge takes support on the opposing portion of the shell base, i.e., that which corresponds to the instep zone, by deforming it, if necessary, so that the resistance opposed by the latter reaches a level that is capable of stopping its the upper in pivoting. As a result therefrom, the bending limit of the upper in these boots is variable as a function of the force applied on the upper and, at any event, it determines an excessive bending amplitude that can be traumatizing for the wearer.
Another disadvantage is related to the difficulty in obtaining a substantial force to resist the forward bending of the upper by simply varying the thickness, height and flexibility of the collar coming from the shell base. Indeed, in view of the fact that this collar is located in the area where the foot passes during the fitting and removal of the boot, it must be sufficiently flexible to move away under the mere pressure from the foot during the passage thereof, without any other intervention; likewise, it must not extend too high in the dorsal zone of the shell base in order not hinder the engagement-disengagement of the heel of the skier's foot, still during the fitting-removal of the boot.
Still another disadvantage is related to the absence of any adjustment, whether for varying the bending stress of the upper, its advance angle, the direction of the resultant force which it transmits toward the shell base, or for the amplitude of its possible bending.
To palliate some of these disadvantages without calling into the question the simplified structure of these boots that are provided with all necessary means to ensure control of the bending, even if they are insufficient as disclosed hereinabove, a known solution consists of using it as a base structure to which means for reinforcing and retaining the upper on the collar are added. That is what is obtained, for example, on the 1972 Lange "PRO", 1982 Caber "Equipe" and 1995 Nordica "Grand Prix" alpine ski boots. Indeed, on these boot models, whose base structure is comparable to that of the previously described boots, the reinforcement is obtained by means of at least two coupling means ensuring a fixed and permanent connection between the upper and the collar. These coupling means are arranged on both sides of the dorsal zone of the heel of the shell base and of the upper, in a symmetrical manner, and in the space comprised between the journal points of the upper and the dorsal zone. With this arrangement of the coupling means, the upper of the boot is blocked, i.e., prevented from any predetermined pivoting, and the bending forces which are applied thereto by the lower part of the skier's leg are thus transmitted in the direction of the shell base with a minimum of power loss and briefly, even quasi instantaneous, because the only bending amplitude of the upper now only results from the deformation of the materials used.
In addition, since the coupling means are located in the dorsal zone of the boot and on both sides thereof, the force resisting the forward bending of the upper is still obtained by a pulling effect, which relatively preserve the tibial zone of the skier's leg. It is obvious that the arrangement of at least two or more coupling means, such as obtained on these boots, makes it possible to reduce the pressures in their location, as well as the risks of deterioration.
Therefore, with respect to the boots previously described, these boots have a substantial bending strength and practically no bending amplitude, which is relatively satisfactory for the experienced skiers but, consequently, these boots are not suitable for all skiers because they are too specific, especially in rigidity, without any possibility of adjustment whether for the bending stress, the advance angle, the bending amplitude, or the direction of the force transmitted to the ski by the inserted shell base.
As a result from the above analysis, the sport boots having a simplified structure as described previously, are generally satisfactory for the user as long as they are used within their specificity, i.e., for spare-time and leisure sport activity or for a very technical sport activity such as competition. Indeed, the reinforcement of the bending strength of the upper of these boots, via fixed and permanent coupling means, cannot be performed by the user of the boot and is not reversible or adjustable for a subsequent adaptation, in view of increasing the bending amplitude of the upper, for example. To satisfy the largest number of users of these boots, it is therefore necessary to provide a large number of models corresponding at least to the various estimated categories of users, and to provide each model with specific characteristics that meet, at best, the requirements of these categories. Obviously, this process is complicated, expensive due to the necessity of having numerous models, and only provides an average technical solution for the user because it is based on a "category of users" and does not really allow for a personalization of the boot.